Male and female Fischer 344 rats and B6C3F1 mice were exposed to 0, 25 or 75 ppm (0, 0.10 or 0.31 mg/l) ethyl acrylate vapors, 6 hours per day, 5 days per week, for a total of 27 months. Additional rats and mice were exposed to 225 ppm (0.92 mg/l) for 6 months and then held for 21 additional months post-exposure. Histopathologic changes in olfactory portions of the nasal mucosa were present in animals in all of these three exposure groups. These microscopic exposure-related changes were concentration-dependent, primarily in terms of distribution of the lesions within the nasal cavity. Generally those areas of the nasal mucosa normally lined by olfactory epithelium were altered, while the regions lined by respiratory epithelium were relatively unaffected. There was no indication of an oncogenic response in any organ or tissue in either rats or mice. A follow-up study in which Fischer 344 rats and B6C3F1 mice were exposed to 5 ppm (0.02 mg/l) for 24-months revealed no treatment-related changes in the nasal mucosa.
Short-term and subchronic vapor inhalation studies have shown that there are pronounced differences in the toxicological properties of ethylene glycol monomethyl ether (EGME) and propylene glycol monomethyl ether (PGME). Overexposure to EGME has resulted in adverse effects on testes, bone marrow and lymphoid tissues in laboratory animals. PGME does not affect these tissues, and instead, overexposure to PGME has been associated with increases in liver weight and central nervous system depression. EGME is primarily oxidized to methoxyacetic acid in male rats, while PGME apparently undergoes O-demethylation to form propylene glycol. Since methoxyacetic acid has been shown to have the same spectrum of toxicity as EGME in male rats, the observed differences in the toxicological properties of EGME and PGME are thought to be due to the fact that the two materials are biotransformed via different routes to different types of metabolites.
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